The inheritance of mitochondria and other subcellular organelles is an essential component of cell proliferation, yet only a few of the proteins mediating this key cellular process have been identified. The goal of this project is to identify and characterize mechanisms that mediatemitochondrial inheritance. The central focus of the combined genetic and biochemical approach is the identification of proteins that mediate the transmission of mitochondria to dughter cells, regulate mitochondrial morphology, and facilitate division of the organelle during mitotic growth. These investigations will employ the budding yeast, Saccharomyces cerevisiae, and fission yeast, Schizosaccharomyces pombe, as model cellular systems. The first specific aim is to identify and characterize products of MDM13, MDM15, MDM16, and MDM17, four cerevisiae genes defined by newly isolated mdm mutants which display conditional defects in mitochondrial distribution and morphology. These MDM genes will be cloned and analyzed and their products will be localized in wild-type and mutant cells using immunological and microscopic techniques. The second specific aim is to identify additional Mdm proteins through the isolation and analysis of extragenic suppressors of the previously characterized mutants mdm1, mdm10, and mdm12. The suppressing proteins will be identified via gene isolation and analysis, and the normal function of the suppressors will be investigated through mutagenesis and licalization studies. A third objective is to characterize physical interactions among various Mdm proteins using binding studies, co-sedimentation experiments, and two-hybrid analysis in vivo. The ourth specific aim is to isolate and characterize mutants of the fission yeast, S. Pombe, that display defects in mitochondrial distribution and morphology. Since mitochondrial distribuion in fission yeast depends on microtubules, a fundamentally different mechanism than that operating in budding yeast, analysis of the S. Pombe mutants should identify novel components. The fifth specific objective is to evaluate the function of S. Pombe Mdm12p, the homolog of a protein that regulates mitochondrial sistribution and morphology in Saccharomyces cerevisiae. Biochemical and mutatinal analysis of this protein should leas to insights into mitochondrial inheritance components conserved in all eukaryotic cells. These studies of mitochondrial inheritance will reveal new details of cellular organization and cell division, and provide a foundation for understanding changes in cell structure and function asssociated with numerous disease states.